1. Field of the Invention
The present invention relates generally to railway switching devices and, more particularly, to a railway switch circuit controller for controlling a circuit associated with the railway switching device.
2. Description of the Related Art
Railway turnouts alternatively divert trains from one set of tracks to another set of tracks. A common turnout used in the industry has a switch property which includes: switch points connected to a point detector connecting rod, a switching device or machine that is connected with an operating rod to the point detector connecting rod, a frog to carry the train wheel flanges across opposing rails, and lead rails between the frog and the switch points. In operation, the operating rod transmits the operating force of the switching device to the switch points, thereby causing the switch points to move. The point detector connecting rod follows the movement of the switch points and translates the position of the switch points at all times.
A railway switch circuit controller is a device that is typically mounted to the railroad ties and is connected to the point detector connecting rod. The switch circuit controller provides a signal indicating the position of the point detector connecting rod and related switch points. The signal produced by the switch circuit controller is a vital indication, which means that the signal is considered fail-safe, that the signal need not be checked further, and that the signal may be presumed to be accurate. The signal from the controller is transmitted to a micro-processor controller to identify the position of a crank and the connected point detector connecting rod. A description of a typical railway switch circuit controller may be found in U.S. Pat. No. 5,598,992, issued in the name of Chew, which patent is assigned to the present Assignee and is hereby incorporated by reference herein.
By way of brief description, the typical railway switch circuit controller comprises various mechanical moving parts that operate together such that movement of the point detector connecting rod causes electrical contacts to be made inside a housing of the controller. As described in the above-referenced U.S. Pat. No. 5,598,992, the various mechanical moving parts include a crank arm connected to a rotatable cam shaft that has one or more cam segments that are engageable with one or more movable spring-biased followers. The followers are connected to respective movable electrical heel contacts. Additionally, a contact spring assembly is comprised of two spaced-apart fixed electrical contacts and the movable heel contact. The contact spring assembly is mounted to an insulating terminal board that is mounted within the housing. When the operating rod is thrown by the switching device to move the switch point, the translation of the operating rod and attached point detector connecting rod moves the switch points and causes the connected crank arm to rotate. When the crank arm rotates, the cam shaft rotates, causing the cams to engage the spring-biased followers, which in turn cause various movable contact springs to complete selected electrical circuits, which produce respective electrical signals. Thus, movement of the point detector connecting rod causes electrical signals to be produced by electrical contacts that are made inside of the housing of the controller.
It has been found in the harsh railroad environment that the repetitive cycling between normal and reverse positions of the switch points results in wear and tear on the movable mechanical parts within the controller housing, thereby requiring maintenance on a frequent basis. Replacement of individual mechanical parts may require too much money and maintenance personnel time to be cost-effective. Further, the plethora of such controllers on existing railway lines makes replacement of the plethora of such controllers advantageous if the existing railway switch does not require significant redesign.
Consequently, a need has been felt for providing a railway switch circuit controller which overcomes the problems of wear and tear caused by the cycling between normal and reverse positions of the switch, and also is interchangeable with the current designs of external tie-mounted railway switch circuit controllers.